Apparatus and package for high frequency usages and their manufacturing method

ABSTRACT

A package for high frequency usages  10  has a notched area  16  on each longitudinal end of a substantially rectangular heat sink plate  11  for fastening the package to a base  20  with a screw. The package includes a joined member  17  formed by joining a surface of a ring-like frame member  12  made of a ceramic material to the longitudinal center of a surface of heat sink plate  11  and joining another surface to an external connection terminal  15 . The other surface of heat sink plate  11  presents a curved protruding shape  18  bowing from its longitudinal ends toward its longitudinal center, so that curved protruding shape  18  causes at least an area of the other surface heat sink plate  11  that corresponds to an area dedicated for mounting a semiconductor device  19  within ring-like frame member  12  to make a close contact with base  20  when the package is fastened to base  20  by the screw at notched areas  16.

INCORPORATION BY REFERENCE

[0001] The present application claims priority under 35 U.S.C. §119 toJapanese Patent Application Nos. 2003-163429 filed on Jun. 9, 2003,2003-368371 filed on Oct. 29, 2003 and 2004-020663 filed on Jan. 29,2004. The contents of the applications are incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

[0002] The invention relates to an apparatus and a package for highfrequency usages formed by joining a heat sinking plate with aring-shaped frame member made of ceramics, in particular, where the heatsink plate is affixed to the base plate, and their manufacturing method.

BACKGROUND OF THE INVENTION

[0003] Packages for high frequency usages equipped with high frequency,high power semiconductors such as gallium arsenide field effecttransistors have been used, for example, for RF (radio frequency) basestations. A high frequency semiconductor device generates a lot of heatwhen it is operating, so it may fail to work properly unless thegenerated heat is efficiently dissipated into the air. Therefore, apackage for high frequency uses is typically equipped with a heat sinkmade of a substantially rectangular metal plate to provide a high heatdissipating characteristic with an area for mounting a semiconductordevice. A ring-shaped frame member made of ceramics is joined on theouter periphery of the semiconductor mounting area of the heat sinkplate. The space surrounded by the ring-shaped frame member and the heatsink forms a cavity for storing the semiconductor device.

[0004] After the semiconductor device is mounted on the heat sink plate,the upper surface of the ring-shaped frame is hermetically sealed with acap member that seals the cavity. Also, external connection terminalsare connected between the ring-shaped frame member and the cap memberfor signal input/output. The package for high frequency usages equippedwith a sealed semiconductor is then affixed on the base plate to allowthe heat transmitted to the heat sink to dissipate to the outside.Affixation is done by fastening the notched areas formed on both ends ofthe heat sink plate in the lengthwise direction using screws.

[0005] FIGS. 1(A) and (B) show a typical high frequency package 50 ofthe prior art. Number 51 denotes a heat sink plate having a thermalexpansion coefficient close to that of the ceramic material made of acompound metal material with an excellent thermal dissipationcharacteristic such as copper-tungsten (Cu—W), and number 52 denotes aring-shaped frame member made of a ceramic material such as alumina(Al₂O₃).

[0006] A metallic conductor pattern is formed on the front and backsurfaces of ring-shaped frame member 52. The metallic conductor patternon the back surface of ring-shaped frame member 52 and heat sink plate51 are joined by means of brazing via Ag—Cu brazing metal 53. Externalconnection terminals 54 are joined to the metallic conductor pattern onthe surface of ring-shaped frame member 52 via Ag—Cu brazing metal 53.The brazing process is conducted by heating after placing ring-likeframe member 52 on heat sink plate 51 via Ag—Cu brazing metal 53 andplacing external connection terminals 54 on ring-like frame member 52via Ag—Cu brazing metal 53. The metal surfaces of heat sink plate 51,ring-like frame member 52, and external connection terminals 54 are tobe covered with metallic plating such as Ni plating and Au plating. Anotch 57 is provided on each end of heat sink plate 51 in itslongitudinal direction for fastening heat sink plate 51 to a base plate55 with a screw.

[0007] Similar attempts of prior art include the kind where a sheet ofindium is sandwiched between the heat sink plate and the base plate forimproving thermal conductivity between the heat sink plate and the baseplate, all of which are fastened together with screws (JapaneseLaid-open Publication 2001-230349) or having a protrusion on each of theheat sink plate in its longitudinal direction for fastening with screws(Japanese Laid-open Publication H4-233752).

[0008] However, these packages of high frequency usages of prior art andtheir manufacturing methods have the following problems:

[0009] (1) While the heat sink plate and the external connectionterminals are made of materials whose thermal expansion coefficients aresimilar to that of the ring-shaped frame member, it is difficult tomatch the thermal expansion coefficients of the heat sink plate and theexternal connection terminals perfectly with that of the ring-shapedframe member, so that it generates a stress in the joined area of hightemperature brazing using Ag—Cu brazing metal. Consequently, a bucklingoccurs in the joined member. Since joined members with buckling thatexceeds the tolerance limit cannot be used, it is a common practice toscreen them against such a tolerance limit. More specifically, if thebottom surface of a heat sink plate, which is to be joined to the baseplate, is caused to buckle in a concave shape, a space is createdbetween the base plate and the heat sink when it is mounted on the baseplate, thus affecting the heat dissipation characteristic. Therefore, itis necessary to select only those with convex buckling shapes. Thus, itmandates a selection process and lowers the yield, resultantlyincreasing the cost of the packages for high frequency uses.

[0010] (2) Using an indium sheet between the heat sink plate and thebase plate brings about a cost increase for a package for high frequencyusages because of the high cost of the indium sheet. Moreover, the useof an insertion such as an indium sheet makes the assembly process morecomplicated thus resulting in a cost increase for a package for highfrequency usages.

[0011] (3) When a protrusion is provided at an end of the longitudinaldirection of the heat sink plate, the package size is increased by theprotrusion provided. For this reason, the need for miniaturization isnot met.

[0012] (4) In forming the metallic plating film on the heat sink plateby means of a electrolytic plating method, the thickness of the heatsink plate on both ends tends to become too thick compared to the middleof the plate in its longitudinal direction, thus causing the bottomsurface that is to be joined to the base plate of the heat sink plate tobuckle into a concave shape. This generates a space between the heatsink plate and the base plate when it is mounted on the high frequencypackage on the base plate, resultantly affecting the thermal dissipationcharacteristics.

[0013] The present invention was made under the circumstance and isintended to provide an inexpensive package for high frequency usageshaving an excellent thermal dissipation characteristic.

SUMMARY OF THE INVENTION

[0014] An apparatus or a package for high frequency usages according toone embodiment of the present invention has a surface of a heat sinkplate intended for contacting with a base plate. The heat sink plate hasa convex shape warped along its longitudinal direction. Another packagefor high frequency usages according to an embodiment of the presentinvention has a plated coating formed on the surface of the heat sinkplate intended for contacting with the base plate and the plated surfacehas a convex shape warped along its longitudinal direction.

[0015] Because of the above constitution, these packages for highfrequency usages can provide improved efficiencies in dissipating heatwhen the heat sink plates are fastened on the base plates with screws asthey make close contacts, thus preventing degradations of semiconductordevices they carry.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIGS. 1A and 1B are descriptive drawings of a typical package forhigh frequency usages of the prior art.

[0017]FIGS. 2A and 2B are a plan view and a front view of a package forhigh frequency usages according to a first embodiment of the presentinvention.

[0018]FIG. 3A is a view showing a semiconductor device mounted on apackage for high frequency usages according to the first embodiment ofthe invention, and FIG. 3B is a view of the same package being affixedto the base plate.

[0019]FIGS. 4A and 4B are a plan view and a front view of a package forhigh frequency usages according to a second embodiment of the invention

[0020]FIG. 5A is a view of a semiconductor device mounted on a packagefor high frequency usages according to the second embodiment of theinvention, and FIG. 5B is a view of the same package being affixed tothe base plate.

[0021]FIGS. 6A and 6B are a plan view and a front view of a package forhigh frequency usages according to a third embodiment of the invention.

[0022]FIGS. 7A and 7B are diagrams showing first and second methods ofmanufacturing packages for high frequency usages.

[0023]FIGS. 8A, 8B, and 8C are diagrams showing a third method ofmanufacturing packages for high frequency usages.

[0024]FIGS. 9A, 9B, 9C, and 9D are diagrams showing a fourth method ofmanufacturing packages for high frequency usages.

[0025]FIGS. 10A and 10B are diagrams showing a fifth method ofmanufacturing packages for high frequency usages.

[0026]FIG. 11 is a graph showing the warping value of the heat sinkplate.

PREFERRED EMBODIMENTS OF THE INVENTION

[0027] The following descriptions of various embodiments with referenceto the accompanying drawings should be helpful for understanding of theinvention.

[0028] [First Embodiment]

[0029] As can be seen in FIGS. 2(A) and (B), a package 10 for highfrequency usages according to the first embodiment of the presentinvention has a ring-shaped frame member 12 made of ceramics joined to aheat sink plate 11 by means of brazing using high temperature brazingmaterial 13.

[0030] Heat sink plate 11 consists of a substantially rectangularmetallic plate with a thermal expansion coefficient similar to that ofthe ceramic material used and a high temperature dissipatingcharacteristic for dissipating a large amount of heat generated by thesemiconductor to be mounted on it.

[0031] Also, external connection terminals 15 are joined to the topsurface, which is the other surface, i.e., top surface, of ring-likeframe member 12 for electrically connecting a semiconductor device 19(see FIG. 3(A)) to the outside, by means of brazing using hightemperature brazing material 13. Heat sink plate 11, ring-like framemember 12, and external connection terminal 15 form a joined member 17.

[0032] A notched area 16 is formed on each end of heat sink plate 11 inits longitudinal direction for fastening it to base plate 20 (see FIG.3(B)) with screws 21 (FIG. 3(A) and (B)).

[0033] Semiconductor device 19 is die-bonded in a cavity 14 of package10 for high frequency usages, and semiconductor device 19 connects toexternal connection terminals 15 with bonding wires 22. Next, cavity 14is hermetically sealed by a cap member 23 made of a plastic, ceramic,metallic, or other material to ring-like frame member 12 with a plastic,glass or other adhesive 24 to form a module substrate 25 for highfrequency usages. Notched areas 16 are formed on heat sink plate 11 forinserting screws 21, and module substrate 25 for high frequency uses isfastened to base plate 20 with screws 21. After fastening it with thescrews, the other surface of heat sink plate 11 of package 10 of highfrequency usages has a convex shape 18 so that the part that correspondsto the mounting area of semiconductor device 19 can make a close contactwith base plate 20. Therefore, the heat dissipated from thesemiconductor device to heat sink 11 is efficiently transmitted to baseplate 20.

[0034] [Second Embodiment]

[0035] FIGS. 4(A) and (B) are a plan view and a front view of a packagefor high frequency usages according to a second embodiment of theinvention respectively, while FIGS. 5(A) and (B) are descriptivedrawings of a semiconductor device mounted on a package for highfrequency usages. In the second embodiment, it is similar to the firstembodiment in that the bottom surface of heat sink plate 11 is formedinto a convex shape 18, but a semiconductor device mounting surface 39of the heat sink plate is formed flat. This makes it possible to mountthe semiconductor device on the heat sink plate in a stable manner.

[0036] [Third Embodiment]

[0037] FIGS. 6(A) and (B) are descriptive drawings of a package for highfrequency usages according to a third embodiment of the invention.

[0038] In the third embodiment, the heat sink plate is coated by ametallic plating film 40 consisting of a Cu plating film with athickness of approximately 15 μm. A metallic plating film 40 is formedon one of the main surfaces 38 of heat sink plate 11, which is thebottom surface side of package 10 for high frequency usages consistingof a joined member 17, in such a way that its thickness increases to themid portion in the lengthwise direction so that it protrudes toward thefront side in a convex shape. Therefore, the heat dissipated from thesemiconductor device to the heat sink is efficiently transmitted to baseplate 20.

[0039] Moreover, all metallic surfaces of joined member 17 that areexposed are coated with Ni plating film same as in the first and secondembodiments, and further covered with Au plating film on top of Niplating.

[0040] Next, the method of manufacturing the package for high frequencyusages of the present invention will be described.

[0041] Before we describe each individual method, let us describe theprocesses that are common to all the manufacturing methods.

[0042] Heat sink plate 11, ring-like frame member 12, and externalconnection terminals 15 that constitute joined member 17 are formedrespectively as follows.

[0043] [Forming the Heat Sink Plate]

[0044] Heat sink plate 11 is made of a metallic substance with a thermalexpansion coefficient similar to that of the ceramic material used, forexample, a compound metallic substance of Cu—W group made byimpregnating copper (Cu) into porous tungsten (W), or a Cu—Mo groupalloy consisting of copper (Cu) and molybdenum (Mo). These metals areformed into a rectangular shape using machining or powder metallicmethods. If heat sink plate 11 is made of Cu—W, the thermal conductivityof Cu—W is approximately 230 W/m-k so that it is capable of efficientlydissipating the heat generated by semiconductor device 19.

[0045] [Forming the Ring-Like Frame Member]

[0046] The material that constitutes ring-like frame member 12 can be aninsulating material such as a ceramic, e.g., Al₂O₃. The ring-like framecan be formed as follows: First, add a plasticizer such asdioctylphtharate, a binder such as acrylic resin, and a solvent, e.g.,toluene, xylene, or alcohol to a Al₂O₃ powder containing a proper amountof sintering auxiliaries, e.g., magnesia, silica, or calcia, mix itwell, and defoam it to obtain a slurry with a viscosity of 2000 to 4000cps. Next, form a roll-like sheet with a thickness of, for example, 0.25mm by means of the doctor blade method and the like, and cut it toobtain rectangular ceramic green sheets of an appropriate size. Next,form ring-shaped frame members using one or multiple ceramic greensheets by the punching method. Next, apply with a screen-printing methoda metallic conductive paste consisting of a high-melting point metalsuch as tungsten or molybdenum on one of the surfaces, i.e., bottomsurface, as well as on the other surface, i.e., top surface of ring-likeframe member 12, to form metallic conductor patterns. If multipleceramic green sheets are used, laminate the green sheets first, and thenapply the metallic conductive past on one side of surface as well as onthe other side of surface of the lamination by the screen printingmethod. Sinter the high-melting point metal and the ceramic greensheet(s) in a reducing atmosphere simultaneously to produce aring-shaped frame member 12 having metallic conductor pattern on bothsides. Heat sink plate 11 will be joined to the metallic conductorpattern on one surface by brazing, and external connection terminals 15will be joined to the metallic conductor pattern on the other surface ina downstream step. The thermal expansion coefficient of Al₂O₃ isapproximately 6.7×10⁻⁶/k and the thermal expansion coefficient of Cu—Wis approximately 6.7×10⁻⁶/k, so that they are close to each other, butit is difficult to equalize them.

[0047] [Forming the External Connection Terminal]

[0048] External connection terminals 15, which are to be joined to theother side surface, i.e., the top surface of ring-like frame member 12,are formed a metallic plate, such as KV (Fe—Ni—Co group alloy; productname “Kovar”) or 42 Alloy (Fe—Ni group alloy), whose thermal expansioncoefficients are close to that of the ceramic material used, bymachining, etching, or punching process or other methods. The thermalexpansion coefficient of KV is approximately 5.3×10⁻⁶/k and the thermalexpansion coefficient of Al₂O₃ is approximately 6.7×10⁻⁶/k, so that theyare close to each other, but it is difficult to equalize them.

[0049] Next, the method of manufacturing joined member 17 by joiningheat sink plate 11, ring-like frame member 12, and external connectionterminals 15 will be described.

[0050] [Forming the Joined Member]

[0051] First Plating Process:

[0052] First, apply the first Ni plating consisting of Ni and Ni alloyon the surface of the metallic conductor pattern on both surfaces ofring-shaped frame member 12.

[0053] Brazing Process:

[0054] Next, place a high-temperature brazing material 13 consisting ofan Ag—Cu brazing metal, such as BAg-8 (eutectic alloy of 72% Ag and thebalance consisting of Cu), on one side of heat sink plate 11. Then,place a ring-like frame member 12 on the high-temperature brazingmaterial 13. After that, heat the assembly at the temperature ofapproximately 780-900° C. to joint heat sink plate 11 and the metallicconductor pattern on one side of surface of ring-shaped frame member 12by brazing.

[0055] Next, place a high-temperature brazing material 13 which includesan Ag—Cu brazing metal, such as BAg-8, on the upper surface of ring-likeframe member 12. Then, place external connection terminals 15 on thehigh temperature brazing material 13. After that, heat the assembly atthe temperature of approximately 780-900° C. to joint externalconnection terminals 15 and the metallic conductor pattern on the otherside of surface of ring-shaped frame member 12 by brazing.

[0056] The joining of heat sink plate 11 and ring-like frame member 12and the joining of ring-like frame member 12 and external connectionterminals 15 form joined member 17. Although the joining of heat sinkplate 11 and ring-like frame member 12 and the joining of ring-likeframe member 12 and external connection terminals 15 are performedseparately in the above process, they can be performed simultaneously.

[0057] Second Plating Process:

[0058] Next, apply the second Ni plating on the entire exposed metallicsurfaces of joined member 17, and further apply Au plating on the Niplating to form package 10 for high speed frequency usages.

[0059] [First Method of Producing the Package of High Frequency Usages]

[0060]FIG. 7(A) and (B) are descriptive diagrams showing the method ofmanufacturing a package for high frequency usages related to the firstembodiment. In this manufacturing method, a heat sink plate having aconvex second surface warped along its longitude direction is formed bypressing one side of surface of heat sink plate 11 obtained in saidprocess of “Forming the heat sink plate.”

[0061] First, place heat sink plate 11 across two support rods 29 on aflat base plate 28 consisting of a flat plate. Alternatively, place heatsink plate 11 on a curved base plate 30 having a warped surface as shownin the diagram. Next, press the middle point of heat sink plate 11 asshown in FIG. 7(B) using a pressing member 31 having a cross section ofV-shape, U-shape, or any other shape, which is substantially equal to adesired convex shape 18.

[0062] Assemble heat sink plate 11 formed as described in the above, aring-like frame member, and external connection terminals formed inconventional manners in a method similar to the one described in the“Forming of the joined member” section to form a package for highfrequency usages.

[0063] [Second Method of Producing the Package of High Frequency Usages]

[0064] Packages for high frequency usages according to the firstembodiment can also be obtained by the following manufacturing method aswell. First, joined member 17 is made according to the method describedin the “Forming the joined member” section. Next, press the middle ofthe surface of heat sink plate 11 that is in contact with the ring-likeframe member using pressing member 31 while heating the joined member attemperatures lower than the brazing temperature, i.e., lower thanapproximately 780° C. Since this heating softens high temperaturebrazing material 13 that joints heat sink plate 11 with ring-like framemember 12, and ring-like frame member 12 with external connectionterminals 15, the other surface of heat sink plate 11 can be formed intoa convex shape 18 having a highest protrusion point in the middle of thelongitudinal direction without damaging ring-like frame member 12 madeof a ceramic material. Flat base plate 28 and curved base plate 30 aremade of metal such as stainless steel, and the radius of curvature ofcurved base plate 30 can be selected depending on the size and shape ofheat sink plate 11, preferably in the vicinity of 700-900 mm. Theheating temperature is selectable, preferably within 250-400° C.,according to the size, shape, and type of joined member 17 and the typeof the high temperature brazing material.

[0065] [Third Method of Producing the Package of High Frequency Usages]

[0066] Next, the method of manufacturing the package for high frequencyusages according to the second embodiment will be described belowreferring to FIGS. 8(A) through (C). This is a method of obtaining aheat sink plate having a flat surface on one side and a convex surfaceon the other side formed by means of grinding the heat sink plate insuch a way as described in the “Forming the heat sink plate” section.

[0067] First, as shown in FIG. 8(A), attach to a flat grinding table aresin member 26 consisting of a thermosetting resin material, whosehardness varies between areas at both ends and an area in the middle,and lay on top of said resin member the heat sink plate obtained in the“Forming the heat sink” process. Resin member 26 consists of a highhardness resin, which is harder in the areas where it makes contactswith both ends of heat sink plate 11, and relatively softer in themiddle. Next, grind heat sink plate 11 as shown in FIG. 8(B) using adiamond grit grinding wheel 27 or a similar device. During thisgrinding, a deflection of heat sink plate 11 occurs to cause the heatsink to elude in a direction opposite to the grinding surface. Sinceheat sink plate 11 eludes (deflects) in a lesser amount in the directionof the surface opposite to the grinding surface in the areas where thehardness of resin member 26, more material is removed by grinding inthose areas. In the middle area where the hardness of resin member 26 islower, heat sink plate 11 eludes (deflects) in a larger amount, morematerial is removed by grinding there. Consequently, when heat sinkplate 11 is freed from the constraint applied during the grindingprocess, the ground surface ends up in a convex shape having a highestprotrusion point in the middle of the longitudinal direction as shown inFIG. 3(C). By peeling off resin member 26 attached to heat sink plate11, it completes the manufacturing process for a heat sink plate 11whose surface on the other side is formed into a convex shape 18.

[0068] Assemble heat sink plate 11 formed as described in the above, aring-like frame member, and external connection terminals formed inconventional manners in a method similar to the one described in the“Forming of the joined member” section to form a package for highfrequency usages.

[0069] [Fourth Method of Producing the Package of High Frequency Usages]

[0070] The package for high frequency usages according to the secondembodiment can be manufactured by a method shown in FIGS. 9(A) through(D).

[0071] First, joined member 17 is made according to the method describedin the “Forming the joined member” section.

[0072] Next, a thermoplastic resin layer 32 is formed on a flat fixtureplate 35 as shown in FIG. 9(A). Next, a spacer 33 for supporting bothends of heat sink plate 11 of the joined member is placed onthermoplastic resin layer 32, and places joined member 17 on spacer 33with ring-like frame member 12 looking downward as shown in FIG. 9(A).The height of spacer 33 is set higher than the total height of ring-likeframe member 12 and external connection terminals 15 so that a space canbe created between external connection terminals 15 and thermoplasticresin layer 32.

[0073] Next, press the middle part in the longitudinal direction of theother main surface of heat sink plate 11 using a press and the like asshown in FIG. 9(B) to bend joined member 17 with spacer 33 as thefulcrum, heat thermosetting resin 32 to make it softer, and fillthermosetting resin 32 into a gap between joined member 17 and fixtureplate 35. Thermosetting resin 32 softens and increases its fluidity whenit is heated, so that it not only fills the gap between joined member 17and fixture plate 35 but also covers the circumference of joined member17 and spacer 33. This pressing and heating causes the other mainsurface of heat sink plate 11 to cave in from both ends of itslongitudinal direction toward the middle part thus creating a concaveshape having a lowest point in the middle part. After the above process,it is returned to the normal temperature while it is being pressed tocause the thermoplastic resin to harden, after which the pressure isremoved. Joined member 17 is affixed on fixture plate 35 while heat sinkplate 11 is warped in a concave shape.

[0074] Next, as shown in FIG. 9(C), let the grinding wheel, which isrotating at a high speed, of a grinding machine 34 to travel overhorizontally over the other main surface of heat sink plate 11 placed onthe table, or let the table to travel horizontally relative to thegrinding wheel, which is rotating at a high speed, in order to generatea flat surface with this grinding process. This grinding process is notlimited to the use of grinding machine 34 equipped with a grinding wheelas shown above, but can be replaced by any other metal cutting processsuch as using a milling machine, or by lapping process using abrasivegrits.

[0075] Next, heat thermoplastic resin 32 to soften it and remove joinedmember 17, which is affixed on fixture plate 35 with thermoplastic resin32 from fixture plate 35 as shown in FIG. 9(D). Joined member 17, whichhas contained the deflection generated by the pressure from the othermain surface of heat sink plate 11, releases the deflection as it isremoved from fixture plate 35 and causes its other main surface of heatsink plate 11 to protrude from both ends of the longitudinal directiontoward the middle part, thus generating a convex shape 18 having amaximum protruding point in the middle part. Thermoplastic resin 32adhered to joined member 17, fixture plate 35, and spacer 33 is peeledoff and removed with solvent and peeling liquid. Thermoplastic resin 32can be easily peeled off and removes as it has an excellent peelingcharacteristic. In package 10 for high frequency usages produced in sucha way as described in the above, the other main surface of heat sinkplate 11 has a convex shape 18 that protrudes from both ends towards themiddle and has its highest protruding point in the middle, so that itcan make a close contact with base plate 20 and has an improved heatdissipation characteristic.

[0076] [Fifth Method of Producing the Package of High Frequency Usages]

[0077] FIGS. 10(A) and (B) are drawings for describing the method ofmanufacturing the package for high frequency usages according to thethird embodiment of the present invention. In this method, metal platingfilm 40 is formed according to the following method on the heat sinkplate obtained in the “Forming the heat sink plate” process.

[0078] First, heat sink plate 11 is attached to hooks 44 of a platingrack 43. Next, a dummy member 42, i.e., a metallic plate made ofstainless steel and the like, which serves as a sacrificial electrode tobe connected to a cathode electrode 41, is provided in the vicinity ofeach end in the longitudinal direction of heat sink plate 11 betweenheat sink plate 11 and plating rack 43 in such a way that it essentiallyfaces against the main surface of heat sink plate 11. Heat sink plate 11and dummy member 42 are both held in place by hooks 44 that are mountedon plating rack 43, and plating rack 43 forms cathode electrode 41. Heatsink plate 11 and dummy member 42 are immersed into a plating bath 45together with plating rack 43 as shown in FIG. 10(B). In this platingbath 45, metallic members 47 that are connected with anode electrode 46are provided on one side or both sides of a position where heat sinkplate 11 and the main surface of dummy member 42 are facing each other.In the electrolytic plating method, metal plating film 40 is formed bycausing metallic ions in plating bath 45 to deposit on heat sink plate11 and dummy member 42 on the side of cathode electrode 41 by feedingelectricity through plating rack 43. In the electrolytic method, it alsocauses metallic member 47 on the side of anode electrode 46 to eluteinto plating bath 45 by feeding electricity to anode electrode 46, whichis done simultaneously with electricity feeding to cathode electrode 41.The thickness of metallic plating film 40 deposited on heat sink plate11 is affected by metallic films deposited on dummy members 42 locatedin the vicinities of both ends of the longitudinal direction of heatsink plate 11 and hence varies along the lengthwise direction of heatsink plate 11. This makes it possible to make the plating film thicknessin the middle of the lengthwise direction of heat sink plate 11 thickerthan the plating film thickness on both ends in the longitudinaldirection.

[0079] In order to control the thickness of metal plating film 40 on oneof the main surfaces of heat sink plate 11, which is the bottom side ofpackage 10 for high frequency usages, it is preferable to form metalplating film 40 by providing dummy member 42 between one of the mainsurfaces of heat sink plate 11 and metallic member 47 that faces saidface. If metal plating film 40 formed on heat sink plate 11 consists ofa Cu plating film, pyrophoric acid bath or copper sulfate batch isgenerally used as the plating bath, while phosphoric copper is used asmetallic member 47.

[0080] Assemble heat sink plate 11 formed as described in the above, aring-like frame member, and external connection terminals formed inconventional manners in a method similar to the one described in the“Forming of the joined member” section to form a package for highfrequency usages.

[0081] [Examples of Practical Embodiments]

[0082] The inventor prepared a heat sink plate starting with a flat heatsink plate made of Cu—W with external dimensions of 40×10 mm and athickness of 1.6 mm, keeping one surface flat, and machining the othersurface, which is to be made to contact with the base plate of the heatsink plate, into a convex shape protruding from both ends of thelengthwise direction of the heat sink plate towards the middle area sothat its maximum protruding point lies in the middle area. The inventoralso prepared a ring-like frame member made of Al₂O₃ with externaldimensions of 31×9.5 mm, internal dimensions of 27.5 mm×6 mm, and athickness of 0.25 mm as well as four external connection terminals madeof KV with external dimensions of 11.5 mm×5 mm and a thickness of 0.15mm. The inventor brazed one surface of the heat sink plate with onesurface of the ring-like frame member and another surface of thering-like frame member with the external connection terminals usingAg—Cu brazing metal consisting of BAg-8 to form the package for highfrequency usages of the first embodiment.

[0083] The inventor also prepared a heat sink plate by starting with aflat heat sink plate made of Cu—W with external dimensions of 40×10 mmand a thickness of 1.6 mm, laying the heat sink plate on a curved baseplate having a radius of curvature of 800 mm, and pressing from onesurface of the heat sink plate so that the other surface of the heatsink plate is formed into a convex shape protruding from both ends ofthe longitudinal direction of the heat sink plate towards the middlearea so that its maximum protruding point lies in the middle area. Theinventor also prepared, similar to the case of the embodiment 1, aring-like frame member made of Al₂O₃ with external dimensions of 31×9.5mm, internal dimensions of 27.5 mm×6 mm, and a thickness of 0.25 mm aswell as four external connection terminals made of KV with externaldimensions of 11.5 mm×5 mm and a thickness of 0.15 mm. The inventorbrazed one surface of the heat sink plate with one surface of thering-like frame member and another surface of the ring-like frame memberwith the external connection terminals using Ag—Cu brazing metalconsisting of Bag-8 to form the package for high frequency usages of thesecond embodiment.

[0084] The inventor also prepared a flat heat sink plate made of Cu—Wwith external dimensions of 40×10 mm and a thickness of 1.6 mm, aring-like frame member made of Al₂O₃ with external dimensions of 31×9.5mm, internal dimensions of 27.5 mm×6 mm, and a thickness of 0.25 mm aswell as four external connection terminals made of KV with externaldimensions of 11.5 mm×5 mm and a thickness of 0.15 mm for the purpose ofcomparison. The inventor brazed one surface of the heat sink plate withone surface of the ring-like frame member and another surface of thering-like frame member with the external connection terminals usingAg—Cu brazing metal consisting of BAg-8 to form the package for highfrequency usages of the prior art.

[0085] The warping occurrence rate of the other surface, which is thebottom surface, of the heat sink plate before and after the brazingoperation was measured for 10 samples each of the first embodiment, thesecond embodiment, and comparison example. The measurement result isshown as a line graph in FIG. 11. The range of each arrow in thevertical axis shows the range of fluctuation of each warping measurementvalues in each case. If the value of a warping value is positive, itrepresents a convex warp, while if the value of a warping value isnegative, it represents a concave warp.

[0086] All measurements in the first and second embodiments indicatedconvex warps and the heat sink plate was confirmed to be solidly incontact with the base in all of them, so that it was confirmed thatmaking the other surface of the heat sink plate is effective in assuringa good contact. On the other hand, both convex and concave warps existedin a mixed manner and the warping values fluctuated more substantiallyin case of the comparison cases. It was confirmed further that thosewith concave warps generated gaps in the joining area with the base andthe contact is generally poor.

[0087] Hence obvious changes may be made in the specific embodiment ofthe invention described herein, such modifications being within thespirit and scope of the invention claimed, it is indicated that allmatter contained herein is intended as an illustrative and not aslimiting in scope.

What is claimed is:
 1. A package for high frequency usages comprising: aheat sink plate having a first surface provided with a semiconductordevice mounting area and a second surface of a convex shape curved alonga longitudinal direction; a ring-like frame member made of ceramichaving a first surface for joining to the first surface of said heatsink plate to surround said semiconductor device mounting area and asecond surface situated on the opposite side of said first surface;external connection terminals for joining to the second surface of saidring-like frame member; and a means provided at both ends of said heatsink in its longitudinal direction for affixing the heat sink to a baseplate while maintaining the second surface of the heat sink in closecontact with the base plate.
 2. A package for high frequency usagesclaimed in claim 1, wherein said means for affixing is a notch throughwhich a screw is inserted.
 3. A package for high frequency usagescomprising: a heat sink plate having a first flat surface provided witha semiconductor device mounting area and a second surface of a convexshape curved along a longitudinal direction; a ring-like frame membermade of ceramic having a first surface for joining to the first surfaceof said heat sink plate to surround said semiconductor device mountingarea and a second surface situated on the opposite side of said firstsurface; external connection terminals for joining to the second surfaceof said ring-like frame member; and a means provided at both ends ofsaid heat sink in its longitudinal direction for affixing the heat sinkto a base plate while maintaining the second surface of the heat sink inclose contact with the base plate.
 4. A package for high frequencyusages claimed in claim 3, wherein said means for affixing is a notchthrough which a screw is inserted.
 5. A package for high frequencyusages comprising: a heat sink plate having a first surface providedwith a semiconductor device mounting area and a second surface beingplated, and said plated second surface forming a convex shape curvedalong a longitudinal direction; a ring-like frame member made of ceramichaving a first surface for joining to the first surface of said heatsink plate to surround said semiconductor device mounting area and asecond surface situated on the opposite side of said first surface;external connection terminals for joining to the second surface of saidring-like frame member; and a means provided at both ends of said heatsink in its longitudinal direction for affixing the heat sink to a baseplate while maintaining the second surface of the heat sink in closecontact with the base plate.
 6. A package for high frequency usagesclaimed in claim 5, wherein said means for affixing is a notch throughwhich a screw is inserted.
 7. A method of manufacturing a package forhigh frequency usages comprising: A) preparing a heat sink plate havinga first surface and a second surface situated on the opposite side ofsaid first surface; B) forming the second surface of said heat sinkplate into a convex surface curved along its longitudinal direction bypressing the first surface; C) joining one of the surfaces of aring-shaped frame member made of ceramic to the first surface of saidheat sink plate; and D) joining external connection terminals to theother surface of said ring-like frame member.
 8. A method ofmanufacturing a package for high frequency usages comprising: A)preparing a heat sink plate having a first surface and a second surfacesituated on the opposite side of said first surface; B) joining bybrazing one of the surfaces of a ring-shaped frame member made ofceramic to the first surface of said heat sink plate; C) joining bybrazing external connection terminals to the other surface of saidring-like frame member; and D) forming the second surface of said heatsink plate into a convex shape curved along its longitudinal directionby pressing the heat sink plate from the first surface side whileheating it at a temperature lower than the temperature of said brazingjunction.
 9. A method of manufacturing a package for high frequencyusages comprising: A) arranging a heat sink on a flat resin layer, saidresin layer comprising a hard resin layer that contacts at both ends ofthe heat sink plate in its longitudinal direction and a softer resinlayer that contacts the heat sink plate in the middle; B) grinding thesurface of said heat sink plate along its longitudinal direction,wherein the amount of grinding is larger at each end of the heat sinkplate in its longitudinal direction as an eluding motion of the heatsink plate into the resin layer is smaller and the amount of grinding issmaller in the middle of the heat sink plate as the eluding motion isgreater, thus forming a convex surface that curves along itslongitudinal direction when the grinding is done; C) joining a firstsurface of a ring-shaped frame member made of ceramic to the surfaceopposite to the ground surface of said heat sink plate; and D) joiningexternal connection terminals to a second surface of said ring-likeframe member.
 10. A method of manufacturing a package for high frequencyusages comprising: A) forming a joined member wherein a first surface ofa ring-like frame member made of ceramic is joined to a first surface ofa heat sink plate, and external connection terminals are joined to asecond surface of said ring-shaped frame member situated on the oppositeside of the first surface; B) forming a thermoplastic resin layer on afixture plate; C) arranging two spacers separated by a predeterminedspace on said thermoplastic resin layer; D) placing said joined memberon said two spacers so that the ring-shaped frame member is locatedbetween the two spacers, wherein a gap is formed between the externalconnection terminals and the thermoplastic resin by setting the heightof the spacers greater than the total thickness of the ring-shaped frameand the external connection terminals; E) warping said joined member bypressing the middle of said heat sink plate, and filling said gapbetween the joined member and said fixture plate with said thermoplasticresin after softening the thermoplastic resin by heating; F) hardeningsaid thermoplastic resin by taking it back to the normal temperaturewhile maintaining it under the pressed condition, and joining saidwarped joined member to said fixture plate; G) flatly grinding a secondsurface of said heat sink plate; H) forming the second surface of saidheat sink plate into a convex surface curved along its longitudinaldirection by releasing the warping of said joined member by softeningsaid thermoplastic resin by heating; and I) peeling and removing saidthermoplastic resin.
 11. A method of manufacturing a package for highfrequency usages comprising: A) preparing a heat sink plate having afirst surface and a second surface; B) providing a metal plating coat onsaid heat sink plate by the electrolytic plating method comprising thefollowing a, b, and c processes: a. connecting the heat sink plate to acathode electrode; b. placing a metal dummy member connected to thecathode electrode in a vicinity of each end of the second surface of theheat sink plate in the longitudinal direction; and c. platingelectrolytically the heat sink plate and the dummy member, forming aconvex-shaped plating surface on the second surface side, and saidsurface curving along its longitudinal direction; C) joining one of thesurfaces of a ring-shaped frame member made of ceramic to the platingsurface of the first surface; and D) joining external connectionterminals to the other surface of said ring-like frame member.
 12. Anapparatus for high frequency usages comprising: a heat sink plate havinga first surface provided with a semiconductor device mounting area and asecond surface of a convex shape curved along a longitudinal direction;a ring-like frame member made of ceramic having a first surface forjoining to the first surface of said heat sink plate to surround saidsemiconductor device mounting area and a second surface situated on theopposite side of said first surface; external connection terminals forjoining to the second surface of said ring-like frame member; a baseplate; and a means provided at both ends of said heat sink in itslongitudinal direction for affixing the heat sink to the base platewhile maintaining the second surface of the heat sink in close contactwith the base plate.
 13. An apparatus for high frequency usages claimedin claim 1, wherein said means for affixing is a notch through which ascrew is inserted.